This invention relates to a mechanism for conversion between rotary and linear motion, and more particularly to such a mechanism in which a wire or shaft is held between rotatable rollers, the rotational axes of the rollers forming an angle with the wire.
It is an object of the present invention to provide an improved mechanism for conversion between rotary and linear movement which is simple and inexpensive to fabricate and does not have high frictional losses.
Most conventional mechanisms for conversion between rotary and linear motion are dependent upon various types of gears, the most common being rack and pinion arrangements. Many such devices are characterized by high fabrication expenses associated with the cutting of gear teeth and the close tolerances required. In addition, there are often undesirable lubrication requirements and high frictional losses. Another problem associated with the use of such gears is backlash. Moreover, many prior art devices are capable of moving through only a relatively short linear path before they must be interrupted and recycled. Others are not suitable for relatively fine adjustments.
An improved solution to the problem of conversion between linear and rotary motion is disclosed in U.S. Pat. No. 3,081,639 issued to Murray L. Hauptman on Mar. 19, 1963 and entitled "Feed Mechanism."
In the Hauptman device, a shaft is advanced by rollers disposed at an incline or angle to the rotational axis of the shaft. A difficulty is encountered, however, in applying this principle to a relatively thin wire because more than two rollers of suitable diameter will interfere with each other before they engage the wire. (The term wire is used herein to refer to any small diameter shaft or cable regardless of its flexibility or the use to which it is put that presents the problem of not being readily engageable by more than two rollers simultaneously.)